The Outriders are one of the two divisions of the Courier's Guild. They are responsible for delivering messages or packages of the utmost importance, wherever they need to go. The Unicorn Post only delivers to the Five Nations, and only to relatively civilised areas. The Outriders cover everywhere else, no matter how remote or dangerous.
There is no standard rate for an Outrider delivery; the costs will be set on a case by case basis, reflecting the supplies, staff, and dangers of the mission.